With development of electronic industry, many circuits demand stable controllability in addition to their original functions. For example, in order to determine the current of the inductor inside a boost converter circuit, some related professionals in the art cascade a Hall device to the inductor to measure the inductor current. However, the Hall device normally has larger volume and occupies more layout space, which is unfavorable to the present requirement of miniaturizing electronic devices. Besides, the Hall device is more expensive and would raise the cost of the circuit.
A U.S. Pat. No. 9,325,235 disclosed another technology. From FIG. 4 of the specification of the patent, it is learned: a current transformation element is cascaded to one end of an active switch, which is adjacent to an inductor, to sense the current. However, the active switch of a boost converter circuit is controlled by a driving signal to turn on or off. While the active switch is turned on, the related loop is in a connection state, allowing the current to normally flow through the current transformation element and enabling the current transformation element to acquire a sensation signal. While the active switch is turned off, the related loop is in a disconnection state, prohibiting the current from flowing through the current transformation element and disabling the current transformation element from acquiring the sensation signal. Thus, the current transformation element cannot sense the complete inductor current but can only sense the current while the active switch is turned on.